1. Can copper-clad steel replace solid copper in an earthing grid?

Yes, provided two things are done by the book: the copper thickness is chosen from soil corrosion rate × design life (the anti-corrosion standards Q/GDW 12015 and DL/T 2094 and the supervision guide DL/T 2650 agree: 0.25 / 0.6 / 0.8 mm for low / medium / high), and the cross-section is checked for fault-current withstand per IEEE Std 80-2013 clause 11.3.1 with the material constants for the actual conductivity. With both satisfied, copper-clad steel can be used for horizontal and vertical electrodes alike, which is what Chinese national codes and grid-company standards have specified for twenty years. Where it cannot, we say so: extremely corrosive soil combined with a long design life (required copper over 1.0 mm), and 330 kV and larger hub substations (fault current ≥ 50 kA, required section ≥ 240 mm²) – there solid copper or a hybrid grid is the right answer. See "Where CCS can replace solid copper" on the thick-layer page.

2. What is the difference between copper-bonded (electroplated) and continuous-cast copper-clad steel?

Different process, different achievable copper thickness, different final temper. Electroplated: electrodeposited copper, usually 0.25 mm (0.13 mm also on the market), supplied hard – a mature product for driven vertical rods, which we supply too; 0.25 mm-class plated round conductor for horizontal laying also exists in North America – in utility substations and lightning down-conductors outside the NEC's scope; the NEC itself still requires a bare-copper ground ring. Continuous-cast: the steel core passes through molten copper and takes a metallurgically bonded thick layer, 0.25–1.0 mm as specified, which can be fully annealed to a soft temper – the right product for horizontal conductor bent and laid on site. Pressure-bonded / hot-roll clad (the "copper-clad steel wire" of IEEE 80 Table 2) is a third family, mostly used for strand wires. All three are called copper-clad steel in English, so a specification must state the process, the minimum copper thickness at any point and the temper separately – "copper-clad steel, 30 % IACS" on its own specifies nothing.

3. How thick should the copper layer be?

Thickness = corrosion loss over the design life + the layer that must remain at end of life (taken as 0.25 mm). The allowance is calculated per DL/T 2094; where no local data exist, the rates of DL/T 1312-2023 Table 1: negligible 0.001 / weak 0.003 / medium 0.007 / strong 0.012 / extreme 0.017 mm per year, with soil of pH < 4.5 moved up one class (same clause). The standards' resulting classes are 0.25 / 0.6 / 0.8 mm for low / medium / high (Q/GDW 12015, DL/T 2094, DL/T 2650 Table 4). Examples: medium, 30 years: 0.007 × 30 + 0.25 = 0.46 → 0.6 mm; strong, 40 years: 0.012 × 40 + 0.25 = 0.73 → 0.8 mm; extreme, 40 years: 0.017 × 40 + 0.25 = 0.93 → 1.0 mm; extreme, 50 years → 1.1 mm, beyond copper-clad steel – we recommend copper. The soil class is judged from resistivity, pH, salt (chloride) content and moisture; in the assessment we state the class and the basis from the soil data you send.

4. Copper-clad steel is only 25–40 % IACS – will the grid resistance go up?

Grid resistance to remote earth is set by soil resistivity and grid geometry; the conductor's own resistance is negligible in that calculation – the IEEE 80 grid-resistance formulas contain no conductor-material term. Conductivity governs something else: the cross-section needed for fault-current thermal capacity. The simplified formula of IEEE 80 clause 11.3.1, A_kcmil = I_kA · K_f · √t_c, handles it through K_f: copper 7.00, 40 % copper-clad steel 10.45, 30 % copper-clad steel 12.06 – for the same fault current and clearing time, 30 % CCS needs about 1.7 times the section of copper. Example, 20 kA for 1 s: copper 140 kcmil ≈ 71 mm², 40 % CCS 209 kcmil ≈ 106 mm², 30 % CCS 241 kcmil ≈ 122 mm² (1 kcmil = 0.5067 mm²). That is why conductivity must be stated honestly per size (Ø 16 / 0.8 mm is about 27 % – see the calculated table on the Products page): we size with the actual conductivity of each size, not a blanket "30 %".

5. How is the cross-section checked to IEEE 80?

IEEE Std 80-2013 clause 11.3.1 gives two forms: the full equation (37), which yields mm² directly from the material constants, and the simplified A_kcmil = I_kA × K_f × √t_c – its result is in kcmil; multiply by 0.5067 for mm². t_c is the fault clearing time in seconds; I is the design current in that conductor – after the split factor and current division within the grid, not the total system fault current. K_f is taken from Table 2 for the listed materials; for a conductivity not in Table 2 (27 %, say) it is calculated from the material constants (resistivity, temperature coefficient, thermal capacity, fusing temperature) with equations 41–44 of clause 11.3.1. Our assessment gives two options – equal diameter (does the existing diameter pass?) and equal short-circuit withstand (a strict match to the original copper section) – with all intermediate figures, so your consultant can recalculate.

6. Steel is exposed at cut ends and joints – is there galvanic corrosion?

Yes, and this is the real weak point of copper-clad steel – it is handled by the joint, not by the conductor. The exposed steel area is small and the surrounding copper area large: a large cathode with a small anode, so the exposed steel corrodes locally and fast. The remedies: ① exothermic welding – the copper alloy fully encloses the conductor end (DL/T 1342-2014 requires the weld to enclose the end faces of the parent conductor completely), so the cut no longer touches soil; ② mechanical connections – seal the end with an epoxy or bituminous coating before burial; ③ never bury a bare cut end, and treat every conductor cut short on site the same way. This is why we supply the moulds and powder and attend the first joints on site. CCS to solid copper: copper on copper, no couple while the layer is intact. CCS to galvanized steel structures: exactly the situation of a copper grid (copper is cathodic to zinc and steel) – handled by normal practice.

7. What if the copper layer is scratched during installation?

A scratch down to the steel is the cut-end case again – local exposed steel corrodes faster, so clean and coat it. Prevention rests on two things: a thick layer resists handling damage (0.8 mm of copper is not 0.25 mm of plating), and an annealed layer does not crack on bending – the DL/T 1312 bend test (horizontal conductor 90° × 3 with no cracking) checks exactly that. Hard, thin-layer rod material tends to crack on the outside of a site bend, which is why we do not recommend hard rod stock for horizontal electrodes.

8. Which soils are unsuitable for copper-clad steel?

"Extreme" soil as DL/T 1312-2023 Table 1 defines it (high class plus pH > 8.5 or < 4.5 and salt > 1.5 %) – for which that standard calls for copper – and long design lives needing more than 1.0 mm of copper: tidal coastal ground, high-chloride saline soil, and acidic soil that lands in "extreme" after the pH < 4.5 upgrade – where the required copper exceeds 1.0 mm we recommend solid copper. Stray-current environments (DC traction, cathodic-protection interference) need a separate assessment: stray-current corrosion attacks copper and copper-clad steel alike, and the copper on CCS is finite. For such projects the assessment report states the conclusion and the basis.

9. Does copper-clad steel reduce theft?

Substantially – it is one of the main reasons utilities have switched. Copper is only about 20 % of the weight (Ø 16 / 0.8 mm: about 0.34 kg of copper in 1.62 kg per metre) and is metallurgically bonded to the steel, so it cannot be stripped and has little scrap value – nothing to attract a copper thief. Copper grids dug out in whole sections, leaving a substation without its earth, have happened in several countries.

10. Which standards apply, and what do your reports cover?

Sizing: IEEE Std 80-2013 (cross-section and K_f), GB/T 50065-2011 (China). Product: DL/T 1312-2023 – the dedicated standard for copper-clad steel earthing conductor, with a power-frequency high-current test and a 500 h salt-spray sequence; our CMA / CNAS dual-stamped type-test reports cover its full programme. United States: UL 467 (listing of rods, clamps and connectors), ASTM B910 (copper-clad steel ground rods), ASTM B227 / B228 (copper-clad steel wire and strand). Lightning-protection components: IEC 62561-2. European substations: EN 50522 / IEC 61936-1. Connectors: IEEE 837, DL/T 1342. The item-by-item comparison is on the Test evidence page.

11. How do we verify copper thickness on delivery?

Per DL/T 1312: on rod or wire, three positions at least 50 mm from an end, three points 120° apart at each, nine points in all, minimum value governs; by the magnetic method (GB/T 4956, identical to ISO 2178) or the microscopical cross-section method (GB/T 6462, identical to ISO 1463). A magnetic thickness gauge does it in minutes, in any laboratory or on site. Each lot (≤ 5,000 m) ships with its factory test report; send a sample to any accredited laboratory, and if it disagrees with our data sheet we pay for the second test.

12. Can it be welded to an existing copper grid?

Yes. CCS-to-copper and CCS-to-CCS joints are exothermically welded with moulds chosen for the two conductor sizes and the same powder as copper-to-copper. Acceptance per DL/T 1342-2014: the weld fully encloses the parent conductor, DC resistance not more than 1.1 times an equal length of parent conductor, tensile strength not below the parent; for US-specification projects connectors can be required to IEEE 837. We supply the moulds, powder and procedure, and attend the first joints on site.

13. Lead time, minimum order and payment?

Standard sizes 2 weeks ex-works (sizes that need a type test first: add the test period, about two months); order to port of arrival about 5 weeks South-East Asia, 7–8 weeks the Gulf, about 10 weeks Europe and the US East Coast. Minimum order 300 m for standard sizes (rods 50 pieces), 1,000 m for non-standard sizes. Quoted FOB Shanghai by default; T/T 30 % deposit, 70 % before shipment. See "Supply, capacity and lead time" and "Ordering terms" on the Products page.

14. How does the free assessment work?

Send the conductor size and length, soil data (resistivity, pH, salt / chloride), design fault current and clearing time, and design life; within 24–48 hours you receive two options (equal diameter / equal short-circuit withstand), the basis for the copper thickness, the IEEE 80 section check, and the copper saved in tonnes and dollars, signed by the chief engineer. Request it here.

Tender specification clause – copper-clad steel earthing conductor (paste into your technical specification)

Fill in the square brackets for the project. The clauses follow DL/T 1312-2023, IEEE Std 80-2013 and DL/T 1342-2014 and name the US / IEC equivalents; your consultant can check, cut or amend each one.

Downloads